Research Of CMTS Dual Downstream Channel Technology

With the great development of social productivity, the position of information in the socioety is continually increasing. The human society is entering the information-intensive society gradually, and the information industry will become the leading industry in the world in the 21st century. The broadband optic communications technology has obtained huge advancement, which guarantees that the backbone network has high transmitting bandwidth and strong switch capability. Comparing with the above, the access technology develops much slowly, which becomes the bottleneck of modern information superhighway. To overcome this limitation, various new access technologies have emerged, among which HFC network has gained much more attention for its particular bandwidth feature.This paper firstly studied the following points: topology, frequency range and new services of HFC network; its developing status at home and abroad; its advantages and criteria; current problems and their solutions. Then this paper is investigated the DOCSIS protocol, discussing its protocol stack, the interaction with MAC sub-layer, operation mechanism of MAC sub-layer, and interactive communication process of CMTS between CM.Thereafter, the paper points out the existing limitations of single downstream channel and discusses the implementation of double downstream channel.The latter includes the support of DOCSIS agreement, the concrete scheme of downstream channels , the problem involved in downstream channels,its corresponding solution,and several respects of reciprocation among CMTS and CM have put forward the train of thought of realization of downstream channels in downstream channel systems.And general introduction of the whole software & hardware platform is given as an addition.The focus of this paper is on the research of channel switching and the program design of time stamp synchronization between the double downstream channels. Only after the reason that causes the channel to switch over, could the course switched over to the channel after analyzing the reason causing the channel to switch over be analyzed and designed,that's why the research stressed the channel switches. The key of the design is how to synchronize the time stamps of two downstream channels. The upstream synchronization can be achieved from either of the two downstream channels. Then the paper is presented the concrete scheme and program codes. Finally, the testingresults are given.